Rheumatoid arthritis (RA) is a chronic autoimmune disease of the joints. As well as afflicting the joints, the disease may also affect internal organs and the cardiovascular system. Thus far, the causes of the disease are largely unexplained. For diagnosis, the presence of autoantibodies in a patient's serum is presently used, among other things. In addition to detecting the rheumatoid factor (autoantibodies against endogenous IgG molecules), detecting anti-CCP antibodies, which act against citrullinated side chains of proteins, makes earlier diagnosis of RA possible (Schellekens 1998). A comparably high sensitivity can be achieved by detecting mutated citrullinated vimentin, MCV (Poulsom 2008). Commercial test kits are already available for detecting both anti-CCP antibodies and anti-MCV antibodies, and make possible simple, rapid detection of the antibodies and thus a prediction as to the diagnosis of RA. However, evaluation of the stage of the disease, in particular the state of the joint destruction, is only possible to a very limited extent by detecting the autoantibodies systemically present in the blood.
It is therefore desirable to use RA diagnostics which take into account the activation status of the immune cells involved in the disease. It is known that particular cell populations of the immune cells, such as T cells or monocytes, secrete different cytokines depending on the disease stage of the RA, said cytokines making it possible to make a prediction as to the progress of the RA. It is also known that these cells also circulate in the patient's circulatory system in a small amount.
It has been observed that different cytokine levels can be found in RA patients from in healthy controls as a result of stimulation of suitable signal transduction paths of cells of the immune system. Meusch 2009 states that the signal emission via transmembrane TNF-α (tumour necrosis factor, for which the common abbreviation “TNF-α” is used herein) in monocytes from the RA patient's blood is associated with increased IL-1β formation. For this purpose, monocytes are initially isolated from the patient's blood, counted, and subsequently cultivated at a defined number in cell culture medium in the presence of anti-TNF-α, the IL-1β level subsequently being determined by ELISA.
It is further desirable to be able to make a prognostic prediction as to the disease progression by simple test methods. Prognosis as to a patient's response to a particular form of treatment is particularly desirable.
For clinical use, it is worthwhile to provide easy-to-use test systems and corresponding methods which make it possible to carry out the respectively desired detection in as few method steps as possible, at a low equipment cost but still to a high precision.